Deadlocks vs Deadbolts: What's the Difference and Which Do You Need?

In Australia the terms overlap more than they do in the US: a "deadbolt" is simply a bolt-operated lock, and a "deadlock" is the Australian Standard term for a key-operated deadbolt fitted to an external door. What actually matters for your insurance and your security is not which word you use, it is whether the lock is a key-operated deadlock that meets AS4145.2, the standard most SA home and contents policies quietly require.

What's the actual difference

A standard deadbolt is any lock where the bolt throws straight into the frame rather than angling like a spring latch, which is why it resists being forced or slipped with a card. Some deadbolts are operated by a thumb-turn on the inside and a key on the outside (single-cylinder). A deadlock, in the Australian trade sense, specifically means the bolt is key-operated from both sides, or at minimum meets the AS4145.2 deadlock standard for strength and pick resistance. The jobs we see quoted as "deadbolt installs" and "deadlock installs" in Adelaide are frequently the same physical unit, the difference is in the naming convention the tradesperson or the insurer uses, not the hardware.

Where it genuinely diverges is the single-cylinder vs double-cylinder question, which is the one decision worth getting right for your specific door.

Single-cylinder vs double-cylinder: which you need

A single-cylinder deadlock has a keyhole outside and a turn-knob inside. A double-cylinder deadlock needs a key on both sides, including from inside the house. Double-cylinder units are the stronger choice on doors with glass panels or sidelights nearby, because a thumb-turn within reach of broken glass defeats the whole point of the lock. That is the scenario locksmiths flag most often on Adelaide period homes: a beautiful leadlight front door with a single-cylinder deadbolt and a thumb-turn sitting 20cm from the glass.

• Single-cylinder: fine on solid doors with no glass within reach of the lock, and the safer default for fire egress since anyone inside can exit without a key.
• Double-cylinder: better where glass panels sit near the lock, but it means a key must be kept accessible near the door at all times, out of a burglar's reach but within reach of anyone escaping a fire.

That last point is not a minor detail. SA fire regulations and most insurance assessors expect an occupant to be able to exit an external door without hunting for a key in an emergency. If a double-cylinder lock is fitted, the accepted practice is a key hung on a hook or in a lock box immediately beside the door, never buried in a drawer. A licensed locksmith assessing your door will factor this in rather than just fitting whichever unit is in the van.

Why SA home insurance cares which lock is on the door

Most South Australian home and contents policies have a security clause that requires all external doors to be fitted with a deadlock, or state that a claim following forced entry can be reduced or declined if the door only had a spring latch or a snib lock. The wording varies by insurer, but the pattern is consistent: they want a key-operated bolt lock meeting AS4145.2 on every external door, not just the front. Side doors, garage-to-house doors and sliding doors with a keyed lock are commonly named too, and sliding doors are the one owners most often overlook.

The practical risk is at claim time, not at policy sign-up. Insurers rarely check your locks when you take out cover, they check them after a break-in, when a loss adjuster asks for photos of the point of entry and the lock that was fitted. If that lock does not meet the policy's security definition, the payout can be reduced for underinsurance against the stated condition, even if the rest of the claim is legitimate. Reading your policy's security clause before you need it, rather than after, is the cheap way to avoid that conversation.

What fitting a deadlock costs in Adelaide

Pricing depends on whether the door is pre-drilled for a deadlock (many project-home doors are not) and whether it is a straightforward single-cylinder swap or a double-cylinder unit that needs the internal side keyed too.

Ranges are a typical Adelaide guide, your exact quote depends on the door, the lock brand and whether new drilling is needed. If you are locked out or upgrading multiple doors at once, a residential locksmith can quote the whole job as one visit rather than charging a callout per door.

Getting the right lock fitted for your door

The right choice depends on the door material, whether there is glass nearby, and what your specific policy's security clause actually says, which is worth pulling up and reading rather than assuming. A vetted Adelaide locksmith can assess each external door on the spot and recommend single or double-cylinder per door rather than a blanket rule for the whole house. For the broader picture on securing the rest of the entry, see how to secure your front door and the best door locks for an Adelaide home.